1. Field of the Invention
The present invention relates to an engine mount for supporting an engine or power plant in an engine compartment or the like, and more particularly, to an engine mount which accommodates, rather than suppresses, movement of the engine or power plant arising from torque reactions and the like.
2. Description of the Prior Art
Power producing and power absorbing devices having rotating output and input shafts must be supported in place within their respective structures. Usually, the structure is a machine, and the task becomes both supporting the device, and protecting the balance of the machine from undesirable vibration or other forces originating within the device.
Examples of such devices which are power producers include internal combustion engines and electric motors. Other examples, which encompass power absorbing devices, include air compressors and air conditioning compressors. The forces which originate from the device include torsional, shearing, and axial forces, classified with respect to relationship of the effective direction of the force to the device power input or output shaft. The forces are of greater magnitude in devices having reciprocating pistons, such as piston type internal combustion engines, and piston type compressors, than in devices having pure rotational motion, such as electric motors.
Another factor influencing the magnitude, frequency, and still other characteristics of the undesirable forces is the number of pistons. A single piston device creates the greatest undesirable forces, all other factors being equal. This is because, for each full cycle to be completed, and thus create forces counteracting other forces, two full revolutions of the crankshaft must occur for a four stroke cycle, and one full revolution for a two stroke cycle. As the number of pistons increases, the number of offsetting forces increases for each full revolution, thus muting or offsetting other forces.
In mounting such devices, the prior art generally attempts to address these forces either by suppressing or absorbing them, or by transmitting them to the machine. The latter approach is taken in those few instances wherein power output is more important than longevity of the machine. Examples include race cars, which frequently have engines solidly and unyieldingly mounted to their chassis.
One consequence of this practice is to fatigue the drivers. Under racing conditions, this may be acceptable, but in many other instances, it is not. A motorized appliance, such as a chain saw, may be less desirable to use, less safe, and usable for shorter periods of time, if it imposes this burden on the user. The appliance may therefore provide reduced utility, enjoy less success in the market, and suffer still other disadvantages.
Also, longevity of the device or of certain components will decrease, or the power device may break loose from its associated structure, if subjected to these forces, if the forces are not accommodated properly.
The prior art is replete with many specific situations and proposed solutions, when considering motors and the like.
U.S. Pat. No. 5,221,192, issued to Christopher Heflin et al. on Jun. 22, 1993, exemplifies mounts providing solid rubber feet, and which have metal studs embedded therein. It is a common practice within the air conditioning industry to provide a resilient and elastic pad, in combination with a bolt securing an air conditioning compressor to a supporting structure. A signifcant problem presented by this arrangement, and one addressed by the instant mount, is preventing the bolt from transmitting destructive or undesirable forces from the compressor to the supporting structure.
In U.S. Pat. No. 2,143,739, issued to John J. McCabe on Jan. 10, 1939, a solid block of resilient material surrounds a bushing holding a shaft, instead of a bolt. Shearing and torsional forces are thus resiliently resisted and dissipated.
A pad and bolt type mount which avoids problems arising from the presence of a single bolt passing entire through the pad is seen in U.S. Pat. No. 2,911,170, issued to Robert Galin et al. on Nov. 3, 1959. There are two bolts arranged in line in place of one, each bolt having an enlarged head embedded within the pad. The effect of a single through bolt is provided, but additional flexure is accommodated by provision of two separate bolts, each encased within the resilient pad.
A similar concept is shown in U.S. Pat. No. 2,292,536, issued to John J. McCabe et al. on Aug. 11, 1942.
U.S. Pat. No. 3,018,990, issued to Alfred H. Muller on Jan. 30, 1962, discloses a three point suspension system for an internal combustion engine, employing three bearings of the bolt and pad type.
Bearing assemblies for bearing vertical loads, and for accommodating occasional shear stresses are seen in U.S. Pat. Nos. 4,761,925, and 4,830,927, both issued to Yoshihide Fukahori et al. on Aug. 9, 1988, and May 16, 1989, respectively. The subject bearing assemblies are directed to support of buildings, and resisting earthquakes. The bearings both feature laminations of rigid and elastic plates stacked in repeating patterns. The stack is surrounded by a tubular member for imparting weather resistance. In '927, plural bearings of high and low damping ability are arranged in parallel to provide satisfactory ability to resist an actual earthquake. The instant bearing both isolates its structure from a source of vibration or injurious forces, and damps those forces.
An invention having similar purpose is shown in U.S. Pat. No. 4,887,788, issued to Richard J. Fischer et al. on Dec. 19, 1989. A cylindrical assembly of somewhat complicated internal arrangement of dissimilar elastic, resilient materials is provided. Again, a tubular external member provides environmental protection, and further adds reinforcing strength to the assembly.
U.S. Pat. No. 5,035,395, issued to Brock R. Settlemier et al. on Jul. 30, 1991, describes a cradle assembly built up from components including two stacks of elastic, resilient material.
U.S. Pat. No. 4,335,323, issued to Earl R. Kebbon et al. on Jun. 15, 1982, illustrates a motor bearing opposing both shearing and axial loads imposed upon the output shaft.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.